ixgbe and fast interrupts

John Baldwin jhb at freebsd.org
Thu Nov 17 14:59:58 UTC 2011

On Thursday, November 17, 2011 6:38:21 am Matteo Landi wrote:
> Hi everybody,
> trying to measure the interrupt latency of a 10G Intel network
> adapter, I find out that the the used driver (ixgbe) can can be
> configured to work with both fast and standard interrupts. From my
> understanding of the BUS_SETUP_INTR(9) man page and
> sys/kern/kern_intr.c file, it seems that drivers in need of
> registering fast interrupts should call bus_setup_intr() specifying a
> filter function instead of a handler.
> My question is: why ixgbe_allocate_legacy() says it is allocating a
> fast interrupt (comments and error messages say so) but instead passes
> a handler instead of a filter to pci_setup_intr()? Is there anything I
> am not taking into account?

It is not a fast handler and is not using the fast handler stuff.  OTOH,
you probably want to be using MSI-X for a 10G NIC instead of INTx anyway.

John Baldwin

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